1. Field of the Invention
The present invention relates to a solar cell module with no installation frame, and to an installation method thereof. More specifically, the present invention relates to a solar cell module which has a solar cell reinforcing member, wherein the reinforcing member is also used to install the solar cell module, and which can maintain excellent characteristics without a significant reduction in conversion efficiency. The present invention also relates to a method of installing a solar cell module of this type.
2. Description of the Related Art
In recent years, it has been predicted that an increase in CO.sub.2 in the atmosphere will give rise to a green house effect, which will result in a serious global temperature increase. From this view point, the requirement for development of a clean energy source which does not produce CO.sub.2 has become serious.
Nuclear power generation does not exhaust CO.sub.2. However, it has an unsolved problem regarding the treatment of radioactive wasters, and thus it is required to develop a safer and cleaner source.
Among various candidates for clean energy sources for future use, one of the most promising energy sources is a solar cell, which has advantageous properties in that it is clean, safe, and easy to handle.
There are various types of solar cells. One example is a solar cell module comprising an active solar cell element made up of a single crystal silicon. The active solar cell element used in this type of module is sensitive to mechanical shock. Therefore, it is necessary to protect its surface with a thick glass plate and EVA (ethylene-vinyl acetate copolymer), wherein the EVA fills the space between the active solar cell element and the glass plate.
Another example is a solar cell module comprising an active solar cell element made of non-single crystal silicon formed on a glass plate. This type of module also includes a thick glass plate as in the case of solar cell modules made of single crystal silicon.
In solar cell modules of these types having a glass plate on their surface, it is required to attach a frame to them so as to protect the periphery of the glass plate, to reinforce the mechanical strength of the glass plate, and to connect one module to another module or to install the module on an installation base element.
Materials for the frame include metal, plastic, wood, etc. The weight of a solar cell module having a glass plate is as great as 10 KG/m.sup.2. Therefore, the frame material should have a sufficiently great mechanical strength to support such a great weight. From this view point, extruded hollow aluminum is commonly used.
However, solar cell modules having an installation frame made of aluminum are expensive. Besides, it is not easy to install such a heavy module on a roof or even on the ground. A strong and heavy installation base frame to install the solar cell module is also required, and the solar cell module must be fixed to the base frame with fastening tools including bolts. Thus, the sum of a material cost, installation coast, and base frame cost becomes great.
Among active solar cell elements made of non-single crystal silicon, amorphous silicon solar cell elements have an excellent property in that they have resistance to bending and mechanical shock, and thus they can be formed on a flexible substrate such as high molecular weight plastic or a metal substrate such as a stainless steel foil.
Because the active solar cell element formed on a substrate of this kind is flexible and has strong resistance to mechanical shock, there is no need to use glass as a surface protection material. Instead, a weatherable plastic film such as a fluorine resin film is commonly used for the protection.
However, in practice, a flexible amorphous silicon solar cell is installed on a roof or on the ground, in such a manner that a reinforcing member made of e.g. steel is attached to the back face of the solar cell so as to improve the mechanical strength of the solar cell module to make the installation easy, and then the solar cell module is installed on a strong but heavy base by holding the edge faces of the solar cell module with an aluminum frame or the like.
As a result, while the surface of the amorphous solar cell module is protected with a weatherable plastic film, there is a problem similar to that in the crystalline solar cell module.
As can be seen from the above description, there is a strong demand for developing a solar cell module which has a structural strength sufficient to be easily installed without either an aluminum frame or a heavy base. If a solar cell is produced in an integral form with a metal sheet such as that used for a metal roof, then it will become possible to bend the metal sheet, the filler, and the surface protection film at a portion outside the active area, thereby increasing the structural strength of the solar cell module itself, whereby a frameless solar cell module can be realized.